Early prevention of freezing injury of rapeseed

Rape, also known as oil cabbage, bitter cabbage, Latin name: Brassica campestris L. Cruciferae, Brassica plants, native to China, its stem color dark green, help such as cabbage, cruciferous cabbage varieties, flowers yellow. Agronomically, many species of oil-bearing plants are collectively referred to as rape. At present, the main cultivation (variety) types of rape are: Brassica rapa (campestris) L., Brassica juncea L. , Brassica napus L.

Growing conditions of rape

Temperature requirements: rape is a cold-loving, cold-resistant crops. According to experiments, the lowest temperature for seed germination is 4~6℃, and seedlings can emerge in 4 days under the condition of 20~25℃. The flowering period is 15~19℃, and the pod development period is 12~15℃. Moreover, the temperature difference between day and night is large, which is beneficial to flowering and pod development and increases the accumulation of dry matter and oil.

Water requirements: rape growth period is long, vegetative body is large, the number of fruiting organs is large, so it needs more water. The requirements for water at each growth stage are: the soil moisture should be kept at about 65% of the field water holding capacity during germination and emergence; the field water holding capacity should be 76~85% during bud and flowering; and the field water holding capacity should be 60~80% during pod development.

Fertilizer requirements: According to measurements, the ratio of nitrogen, phosphorus and potassium for each 100 kg rapeseed produced is 1:0.35:0.95, and the demand for the three elements is equivalent to more than 3 times that of cereal crops. In addition, rape is sensitive to trace element boron, and lack of it is easy to cause flowers and not fruits.

Requirements for soil: rape is a straight root crop, roots are more developed, taproot deep into the soil, branches, fine roots, deep soil layer requirements, good structure, rich organic matter, both fertilizer and water conservation, and loose aerated loamy soil, in weak acid or neutral soil, more conducive to increasing yield, improve rapeseed oil content.

Early prevention of rape freezing injury

Rapeseed belongs to Cruciferae, Brassica, annual herb, straight root system, erect stem, less branches, plant height 30~90cm. Freezing injury will bring serious economic benefit loss to rape planting, so how to prevent freezing injury of rape?

Enhanced cold resistance

Different measures should be taken for different seedlings to ensure strong seedlings of rape overwintering. Rape leaves are most susceptible to freezing death during overwintering, resulting in a decrease in the number of branches after the year, which directly affects the yield. Therefore, it is necessary to do everything possible to take root and produce leaves before the New Year. For vigorous seedlings before winter, it can be cultivated about 10 cm deep between rape rows from light snow to winter solstice, cut off part of branch roots, reduce their nitrogen absorption ability, promote the accumulation of sugar and other organic matters in rape plants, so as to improve cold resistance. Pay close attention to cole intertillage and soil blockage to thicken root soil layer, which has certain effect on blocking cold wind attack and improving heat absorption, heat preservation and cold resistance ability, especially after high-foot seedlings cultivate soil, rhizome shortening is beneficial to heat preservation. In cold winter season, especially before low temperature attack, quick-acting nitrogen fertilizer should be controlled to control the growth of rape nutrient area and accumulate waxy layer of rape leaves, which is beneficial to cold resistance.

Early and heavy application of wax fertilizer

Adding phosphorus and potassium fertilizer to wax fertilizer can increase the thickness of waxy layer of leaves. It is best to apply wax fertilizer before the cold wave comes. At the beginning of overwintering, applying pig dung or soil fertilizer between rape rows can increase the ground temperature by 2-3℃, and can also have the effect of applying wax in spring. 1000-1500 kg pig dung manure or 2000-2500 kg soil manure is suitable for general mu application. Potassium can increase the concentration of cell fluid and enhance the cold resistance of cells. Generally, 5-8 kg of potassium chloride and 10-15 kg of calcium superphosphate are applied in furrows or holes per mu. Plant ash is rich in potassium and has strong heat preservation. When the weather suddenly becomes cold and other measures are too late to be implemented, a layer of plant ash can be scattered on rape leaves and fields, which can not only protect leaves, but also increase soil heat absorption performance and improve soil temperature.

timely foliar fertilizer spraying

Spraying phosphorus fertilizer on rape leaves can obviously increase the thickness of waxy layer on rape leaves, and has significant cold resistance effect. Generally, the leaves that are purple due to low temperature can be transformed into normal green after 5 days of spraying phosphorus fertilizer, and can withstand the low temperature attack of minus 5℃. The concrete method is that 2kg of calcium superphosphate or 0.5kg of ternary compound fertilizer is used per mu, 30- 40kg of water is soaked for one week, fertilizer residue is filtered, foliar spraying is carried out, and spraying is carried out once every 7 days, and the key object of spraying is rape field with excessive nitrogen fertilizer. For thinner rape, 0.1-0.2 kg urea can be added to phosphate solution to promote rape leaf growth, so as to improve the ability of leaves to produce waxy layer and enhance cold resistance.